Determining BC/DR Methods Recovery Time Objective – (RTO) Time needed to recover from a disaster How long can you afford to be without your systems Recovery Point Objective – (RPO) Age of the data you want the ability to restore in the event of a disaster Any data created or modified inside your recovery point objective will be either lost or must be recreated during a recovery Network Recovery Objective – (NRO) Time required to recover or fail over network operations Completely Duplicated/ Interconnected hot - site Remote Disk Mirroring Disk Mirroring Shared Disk Single Disk Copy Electronic Vaulting Tape On Tape Back up Off site (trucks) Disk Consolidation More Less Delayed Immediate Mission Critical Applications Amount of Data Recovery Time Importance of Data GDPS/STP Metro Mirror Global Mirror Global Copy Tier 7 Tier 6 Global Mirror for zSeries Tier 4 Critical Non Critical Sumberdari : collaboration.greatplains.net/wiki/images/a/aa/SAN101.ppt

Disaster Recovery Concepts Secs Mins Hrs Days Wks Recovery Point Recovery Time Recovery Point Objective (RPO) – Point in time to which applications data must be recovered to resume business transactions Recovery Time Objective (RTO) – Maximum elapsed time required to complete recovery of application data

Recovery Point Objective (RPO) Business needs drive the technology choice Secs Mins Hrs Days Wks Recovery Point Recovery Time Tape Backup Periodic Replication Asynchronous Replication Synchronous Replication

Recovery Time Objective (RTO) Business needs drive the technology choice Secs Mins Hrs Days Wks Recovery Point Recovery Time Global Clustering Manual Migration Tape Restore Recovery Time includes: Fault detection Recovering data Bringing apps back online

Synchronous Mirroring Receipt acknowledgment is provided by target back to cache of source Ending status is presented to host / server DS3, OC-3/12/48 STM-1/4/16 MAN WAN I/O write received from host / server into cache of source CN 2000 CN 2000 OR OC-3/12/48 STM-1/4/16 Synchronous Mode Synchronous mode is most appropriate for an implementation that requires data at the recovery site to be continuously synchronized to the source. In the event of a disaster, the recovery data is accurate up to the last transaction and is immediately available for use. Synchronous Mode provides mirroring of data between the source disk and the target disk system. In this mode, data is first written to the source system and then to the target system. An acknowledgment must be received at the source before a subsequent host I/O operation is allowed. Source Target I/O is transmitted to the cache of the target

Asynchronous Mirroring Source sends only final set of updates to target I/O write received from host / server is collected into Source DS3, OC-3/12/48 STM-1/4/16 MAN WAN CN 2000 OR Ending status is presented to host / server CN 2000 OC-3/12/48 STM-1/4/16 Source Target SRDF/Asynchronous (SRDF/A) SRDF/A is an innovative approach to asynchronous replication that delivers a consistent and restartable remote copy of production data over extended distances and with minimal impact on host applications. Its unique Delta Set architecture provides efficient utilization of bandwidth requirements while minimizing data exposure without sacrificing performance. Delta Sets are cache-resident collections of dependent writes that have occurred within a specific period of time. Delta Sets also provide effective utilization of bandwidth between sites in two ways: • Locality-of-reference • Sizing communication links to average write workloads With traditional asynchronous solutions, every write must be time-stamped, sequenced, and sent to the remote site. Every write is treated as a discrete write and must be moved over the communication link. Through locality-of-reference, Delta Sets allow data to be rewritten, so only the final set of updates is sent to the remote site. Another bandwidth savings provided by SRDF/A is the ability to size communication links to average write workloads rather than peak workloads. Peak workloads might only occur for a brief period while batch updates are occurring or some other period of time when processing activity is high. Because Delta Sets are collecting the new writes in cache while experiencing locality-of-reference benefits, SRDF/A is able to ride through periods of increased write activity more efficiently. Target receives updates and applies the writes to the volume